Semielliptical spring



June l2, 1923.

G. TERzAGl-'n SEMIELLIPTIGAL SPRINQ Filed Jah. 5, 1922 Patented June 12,1923.

sEMpIELLIPTIoAL SPRING.'

' .Application flied Januailyfs, 1922.

To all whom it may concern: n' a Be it knownV that I, GIULIO TERZAGHI,yaA subjectof the King of Italy,1and resident of 21 via Mondov, Turin,in the Kingdom of Italy, vhave inventedv certain new and usefulImprovements in Semielliptical Springs; and` I do herebyy declare'theffollowing' to be'a..full, clear, and. exact :description ofi theinvention, such as will enable others skilled in the art tto which vitappertainsy to inake and use the same,reference being had totheaccompanying drawings, and v to let.- ters or gures of referencemarkedthe'reon, i which form a part of this speciication.- i f AQvehicle spring would be perfect if its fiexure (namely the increase ofthe radius rofl curvature in `millimeters per unit ofv load) andytheaintensity of stress in'its material were-kept constant.

Itiswell known that, when ya -vehicle is running to the static load. ofthe spring (that can be easily predetermined)V a l-dynamieload'is added,that varies continually withiny Wide limits owing to different causes(for instance unevenness of the road, speed, load conditions of thevehicle, etc.) and may attain instantaneous values exceeding that` ofthe statical load, that can be foreseen but not calculated beforehand.

A perfectly working spring as above set forth cannot therefore berealized, as it ought to change continually its form to lit the stressconditions of eac-h instant.

This invention has for its objectto provide a semi-elliptical springworking approximatively under the conditions of the above ideal spring.It consists of several parts connected with each other in such a way asto successively and automatically absorb the load when this latterincreases. The load on the spring is therefore fractionated and thedifferent spring parts come under stress when required by the load.

The parts of the spring have differentv radii of curvature and areconnected in such a way as to lie close to each other.

Owing to this arrangement the parts of the spring are submitted to vaninitial stress and sudden shocks are prevented during the working ofthespring. t

Further, should the carrier plate of the main part break near thecentral bolt, this would entail no serious accident, as generallyhappens with other kinds of springs, as the u devices while the upperpart 2` (having a Grumo TEZAGH'I, 0F usuaria, frati.

l late'w'ould'still work asrla solid-'secured' 65 .at onel `en'd,.and`therefore 'the -runningof the vehicle would not'bef prevented. 1 In ltheaccompanying fdrawings; y f

Fig. 1 isa side-elevation'partly inf'sectio'n of a springembodyingffthefinvention and 60 under-middle load, that" iswhenitsfupper',y l

auxiliary part is coming into 'action Fig. 2 Shows-aaneenOfiuietonne-angl member -betweenthe two parts forming the' Spring. ..1"I 65 y iew of aniodifi'edlfo'rin-of;

I Fig. 3-isa like l the connecting member...` f Figs. 4, 5, 6, 7are'di@gramsYshowing` (the: mounting andworking of the spring shown inFig', 1 1. l. ani.. f1 70 F`gs. 8, 9, l0,v l1 are'fsimilar' diagramsreferring to'- anotherconstructional fornil having non-elasticconnecting meinbersfof l" lsection according to theload to be absorbedby the spring.

The longer main part `1,-is connected in the usual' way by means of eyes4 tov thev carri-age frame, and the ends of thel upper part 2 areconnected'with the part 1v by` means of straps 6 pivoted to eyes 5.

Between a kbridge piece 9 of said straps'V and the lower face of thepart l is situated a 'spiral spring 7 conveniently provided with a'protecting box l0. A

The mounting and working of this springy are diagrammatically shown inFigs. este 11. In Fig. 4 the two parts 1' and 2 havy ing a differentradius of curvature `'are vshown detachedv'from one another. s Saidparts are centrally connected with each 100 other as shown in Fig. 5,where thespring is mounted and unloaded. I/Vhen the spring 1 `is loadedin a first stage thus bringing the load from a zero value (Fig. 5) .toaV determined value that will be referred t0 as Q (Fig. 6.), only thelower partfl comes under stress owing to the usual fastening greaterradius of curvature) follows the i'iexure of the former remaining closeto it.

In the second stage the stress still acts only on the lower part, but,this latter, resting laterallyon the spiral springs 7, gradually throwsinto action the upper part 2 by means of straps 6.

In the third stage, when a determined value Q1 of the load is attained,the upper part 2 (Fig. 7 comes under stress.

On the contrary, when springing back,

' tlie upper part 2, owing to its curvature,

prevents a sudden return of the lowerk part l to its original position,and assists in damping the vibrations. -Y

The stress ofy the material (in pounds per inch2) of the lower part doesnot increase in proportion to the increase of the load beyond the valueQ1, as. by increasing of the load the upper part 2 comesfgradually intoaction. It is thus impossible to exceed frequently certain limits otunitary load nonpermissible in view of the lifeof material while anearlyuniform elasticity of the spring is maintained.

Owing to the above arrangement the number of plates of a semiellipticalspring can be increased without considerably altering its elasticitythus ensuring a perfect workinv.

cIlig. 3 shows a modified form of the strap, referred to as 1l, adaptedto con nect the parts 1 and 2, the spiral spring being omitted. Thebridge 12 of said strap has a curvilinear shape in order to facilitatethe rotation of said straps about the axis of tlie connecting pin.

Figs. 8 to 'll show 4diagrammatically the mounting 'and working of thespring provided with straps ll similar to those of the firstconstructional form shown in Figs. 4 to 7.

Each part is conveniently formed with the greatest possible number ofthin plates and the number of the parts can be varied Without departingfrom the scope of my present invention.

Claims: l. A semiellipt`ical spring, comprising a main spring, adaptedto directly support the load, an auxiliary spring having a posed betweenthe straps and under side of the main spring.

,In testimony that I claim the foregoing as my invention, I have signedmv name.

